Convicted killer Antonie Dixon has died in Auckland Prison at Paremoremo.
Dixon was due in court on Thursday and was awaiting sentence at a later date after second trial for fatally shooting James Te Aute and severing the hands of two women with a samurai sword while on the drug "P" in 2003.
The Department of Corrections confirmed Dixon, 40, was found dead in his cell on Wednesday night.
It says staff attempted to give immediate medical assistance but he was pronounced dead by ambulance staff.
Corrections is undertaking an initial investigation to determine what happened, but said it appeared that Dixon had suffered self-inflicted injuries.
His death will be investigated by the Prison Inspectorate, which acts independently of Prison Services. A coroner's investigation is also under way.
Barry Hart, the lawyer who acted for Dixon, is also trying to arrange for a pathologist to carry out an independent examination of his body.
Mr Hart says the pathologist will represent Dixon's family, specifically his sister, to ensure that all questions surrounding his death are answered.
Mental health concerns
Mr Hart says he had been concerned at Dixon's mental health for some time and wanted an independent mental health expert to visit him in jail, but this did not happen.
Instead, Mr Hart was briefed by a psychiatrist from the Mason Clinic, who had visited Dixon in jail.
Mr Hart says he was told that everything was under control and Dixon would probably de-stress after his next court appearance.
Mr Hart believes Dixon was let down by prison authorities and mental health authorities and should never have been left in a position where he could harm himself.
On 17 January, Dixon pulled a makeshift weapon on Mr Hart during a prison visit.
Corrections says Dixon was seen to be becoming agitated and trying to remove what prison officers believed to have been a makeshift weapon from his shoe. He had been placed in segregation following that incident.
Dixon had also been accused of attacking other prisoners.